I see I have caused a great derailment of the thread. That was not my original intention though.
The image shows my view of the DF gameplay in a nice functional form:
You start your fort, climb steadily uphill, and then hit some straight cliff(first ambush, first siege, berserk miner from previous fort, first lasher squad, first catsplosion, etc... ). Sometimes you overcome the cliff, sometimes you fall from that cliff too brave it again next season/year/etc..., but you always lose some of your best dwarves(those hanging) and have even more dwarves crippled and slowly dying(those crucified). After eventually overcoming the cliff you see a nice straight path to glory, so you clear up your dead and tread lightly onward, oblivious of the next deadly cliff hidden beyond right border of the image.
now, back to the OP questions:
1. you do not HAVE to employ any or all of the migrants. you can aas well leave them dying outside. Letting them in is marginal in the terms of food and booze they will consume, but can greatly expand your options if anything goes south.
With dozens of miners you will be hollowing out great loads of minerals, with dozens of haulers you will not feel any transportation problems, with dozens of farmers you will export food like air, etc... you can just plug any hole in your fortress with migrant brute force, or just let them party and be happy.
If you start thinking if it a good time to start military - you are probably already late a few seasons. I tend to start military from embark, assining at least two of my starting 7 to train 24x7.
2. you can do it any way you want. no single cure for all ills. value designs are different from efficiency designs. efficiency designs differ from security designs. And beauty designs are quite different altogether, as are themed designs.
As you may have guessed - overall design strategy will greatly impact stockpile layout, sometimes even utilizing "gatling stockpiles" - storing raw materials on the central tile of workshop, ensuring that dwarf des not need to perform a single step to produce something.
You can also assign hotkeys to locations of your choice. This way you will never forget where your farms are.
3. you can butcher turkeys for valuable leather and less valuable meat, bones and skulls. Purchasing wardogs at embark is a marginal thing to do. If you do not have strong reasons to do it - do not do it.
No matter what wiki says - war dogs are never a sufficient protection to your fort. even kobold thieves with copper knives will cut your warhaunds in two with ease. War dogs are usefull as meatshields though, giving you valuable ticks in combat. Even if they often die after a single slash.
4. you should just last through another season. maybe explore how big is your embark? how deep can you dig? how tall can your buildings be? If that is done - try to put reality to the test:if you are a good reader - build everything you read about. If you are bad reader - see what can you design on your own with the tools DF gives you and make a post in the forums describing your findings. For inspiration - check out the sky fort